The executive director of Lao peace advocacy group Legacies of War, Channapha Khamvongsa, says the US bombing campaign caused widespread destruction in Laos, and is still claiming lives.

"Forty years later, people are still being killed and maimed," she said.

"Children that were born two generations after the war are still being harmed. This is a continuing tragedy."

The US has increased its annual funding for bomb clearance and victim assistance to $12 million, but Ms Khamvongsa says more help is needed.

"Since the mid '90s, the US has been providing - up until recently - on average around $2 million per year, which is really not a lot of money considering the scale of the problem," she said.

"We are providing people an opportunity to do the right thing.

"And when there is so much wrong in the world today, who doesn't want to do the right thing and do something that is solvable, something that we can work towards addressing and we can eventually solve? This is so solvable."